Changes in pulmonary function associated with long-term exposure to air-conditioned indoor environments: A comparative cross-sectional study

Abstract

Air conditioning (AC) systems are widely used in modern indoor environments to provide thermal comfort; however, prolonged exposure to cold and dry air may adversely affect respiratory physiology even in healthy individuals. This comparative cross-sectional study evaluated the impact of long-term exposure to air-conditioned environments on pulmonary function parameters in healthy, nonsmoking adults. A total of 400 participants aged 25–45 years were enrolled and divided equally into two groups: 200 regular AC users (≥6 hours/day for at least one year) and 200 non-AC users. Anthropometric characteristics were comparable between the groups. Pulmonary function tests were performed using a standardized spirometer, assessing forced vital capacity (FVC), forced expiratory volume in one second (FEV₁), peak expiratory flow rate (PEFR), FEV₁/FVC ratio, and forced expiratory flow at 25–75% (FEF₂₅–₇₅). The results demonstrated that AC users had significantly lower mean FVC (3.73 ± 0.51 L vs 3.93 ± 0.51 L), FEV₁ (3.05 ± 0.53 L vs 3.25 ± 0.53 L), and FEF₂₅–₇₅ (1.92 ± 0.61 L/s vs 2.02 ± 0.61 L/s) compared to non-AC users (p < 0.05). In contrast, PEFR (620.9 ± 150.8 vs 618.6 ± 147.4 L/min) and FEV₁/FVC ratio showed no meaningful differences between the groups. The observed reductions in FVC and FEV₁ indicate decreased lung volumes, while the decline in FEF₂₅–₇₅ suggests early impairment of small airway function despite preserved large airway patency. These findings highlight that chronic exposure to air-conditioned environments may lead to subtle but clinically relevant alterations in pulmonary function even in asymptomatic individuals. The study underscores the importance of maintaining optimal indoor air quality, including adequate humidity control and regular maintenance of AC systems. Further longitudinal and multicentric studies are warranted to confirm causality and assess long-term respiratory health implications.